1. Field of the Invention
The present invention relates to a storage system, a method of controlling a storage system, and a storage medium having a control program recorded thereon.
2. Description of Related Art
In a storage system including a host computer and a disk array device connected with each other so that they can communicate, there is known a duplication management function which enables duplication of data among logical volumes according to real-time copying.
The duplication management function will be described with reference to FIG. 11A through FIG. 11D. In FIG. 11A, a logical volume 71 (“primary logical volume” hereinbelow) formed on physical storage areas provided by disk drives 25, which serve as storage devices, is a logical volume that can be directly accessed from an operating system 12 (“OS” hereinbelow) running on a host computer 10.
On the other hand, another logical volume 72 (“secondary logical volume” hereinbelow) stores a duplicate of the data stored in the primary logical volume 71 by means of the duplication management function of the storage system.
In response to, for example, an instruction from the user, the duplication management function makes the control state of the primary logical volume 71 and the secondary logical volume 72 change between the “paired state” and the “split state”. In the “paired state”, when the contents of the primary logical volume 71 is updated, the contents of the secondary logical volume 72 will also be updated in a real-time basis so as to ensure consistency between the contents of the primary logical volume 71 and that of the secondary logical volume 72. Note that in the “paired state”, access from another host computer 100 other than the host computer 10 to the secondary logical volume 72 is prohibited.
The “paired state” is cancelled, for example, when a pair split command sent from the host computer 10 by the user's instruction is received by the disk array device 20, and according to this command, the control state of the primary logical volume 71 and the secondary logical volume 72 is changed to the “split state” (see FIG. 11B). In the “split state,” the other host computer 100, which was prohibited to access the secondary logical volume 72, will be allowed to access this secondary volume 72. The other computer 100 will be able to access the secondary logical volume 72 during the “split state” in order to backup data, perform batch processing or data analysis, and so forth. Note that in the “split state,” any update to the primary logical volume 71 from the host computer 10 will not be reflected to the secondary logical volume 72.
In usual operation, data that has not been reflected to the secondary logical volume 72 and that has been generated by updating in the primary logical volume 71 is stored as “differential data.” This differential data is to be used to make the contents of the secondary volume 72 consistent with the primary volume 71 prior to returning to the “paired state”, as will be described later.
When a command to return from the “split state” to the “paired state” (such a command is referred to as a “resync command” hereinbelow) is issued from the host computer 10 to the disk array device 20, the duplication management function will synchronize the contents of both volumes 71, 72 (resync in progress) using the differential data, and then cause transition of the control state of primary logical volume 71 and secondary logical volume 72 to the “paired state”.
As described above, the secondary logical volume 72 in the “split state” may be accessed from an OS 102 running on the host computer 100, and the computer 100 may make use of data in the secondary logical volume 72 to backup data, perform any batch operation or data analysis, and so forth.
During the “split state”, however, the host computer 10, which accesses the primary logical volume 71, may not have access to the secondary logical volume 72 as an independent volume separate from the primary logical volume 71. This is because the OS 12 running on the host computer 10 stores identical logical volume names and data set names in the management information for the primary logical volume 71 and the secondary logical volume 72 that is managed by the duplication management function.
The management information may include VTOC (Volume Table of Contents), catalog information, VSAM (Virtual Storage Access Method) data set, and VVDS (Vsam Volume Data Set) that is the information about the data set of the target of system management, if the OS 12 is one for a mainframe. The management information may be the file system management information if the OS 12 is one for an open system.
From the point of view of, for example, attempting to increase performance and decrease cost for a host computer 10, there exists a need to make the secondary logical volume 72 accessible as a logical volume independent of the primary logical volume 71 from the host computer 10, which manages both the primary and secondary logical volumes 71, 72, and not only from the other computer 100.
In order to make the secondary logical volume 72 accessible as a logical volume independent of the primary logical volume 71, it may be sufficient to configure the logical volume names and data set names described in the management information for the primary logical volume 71 and management information for the secondary logical volume 72 to be different from each other.
Such a technology is known in the art and disclosed, for example, in Japanese Patent Application Laid-open Publication No. 2000-339104.
However, in general, the volume names and data set names are described in a number of locations in the management information. It is very cumbersome to perform settings for each data by using an editor, a tool, etc., and in addition, a human error might occur during the setting. It is not practical to perform setting for volume identifiers and data set identifiers every time a routine job, such as a daily data backup, a daily batch processing, and data analysis, is performed at a regular or irregular interval.